At this stage our engineering team is working to correct some problems with custom resolutions. In the meantime I would encourage the community here to collaborate with previous experiences in regard to this procedure that you are trying to follow.
On this Thread the driver worked:
I tried to find this driver Version: 188.8.131.52.4156, but it doesn't seem to be on your site anymore.
Is there any way I can get this driver from you?
Even though its older, it will at least enable me to run my computer at 50htz.
Thanks in advance
From our end at the following link Drivers & Software you will be able to find the latest drivers, I checked and that version is not available according to our download center. However, I did some research myself and found this Intel HD & Iris Graphics Drivers Version 184.108.40.206.4156 WHQL.
The content on the above site is not controlled by Intel. This information is offered for your convenience and should not be viewed as an endorsement by Intel for the merchants or services offered there.
4K @ 60Hz is achieveable by MST (Multi Stream Transport) which stitches together two streams of half resolution 60Hz output to fill the full 4K monitor. To accomplish this you need a 4K monitor which specifically supports MST in.
4K @ 50Hz is achievable without MST, by the creation of a custom resolution in Intel's own driver (not Microsoft's version) which can be manually installed. However, since Windows 10 this has not been working due to Intel's Windows 10 driver removing the ability to specify the timing standard for a custom resolution. Further details are atthis post on this forum - it remains unsolved with no feedback from Intel.
Intel, please help!